Adhesive tape



Patented Nov. 27, 1951 OFFICE ADHESIVE TAPE Martin L. Schechtman, New Market, N. J., assignor to Industrial Tape Corporation, a corporation of New Jersey No Drawing. Application January 12, 1950, Serial No. 138,257

9 Claims. 1

This invention relates to adhesive coated flexible tapes and sheets and more particularly to metal tapes and sheets that are coated with normally tacky and pressure-sensitive adhesives. This application is a continuation in part of application Ser. No. 30,189, filed May 29, 1948, now abandoned.

Normally tacky and pressure-sensitive adhesive sheets and tapes (hereinafter referred to collectively as tapes) based on fibrous or non-metallic film materials are Widely known and have received considerable commercial development in this and other countries. Metal backed tapes of similar construction were considered in the literature at various times and there were attempts to produce them commerciallyl but in the past development of such products on a commercial scale has not progressed very far. The main cause of this retardation of the development of normally tacky and pressure-sensitive metal tapes was the difficulty of anchoring the normally tacky and pressure-sensitive adhesive to those metals that offered the greatest promise and were most desired as backings, namely, lead, aluminum, and zinc-coated aluminum. Prolonged storage or repeated use of metal tape samples of the prior art resulted frequently in separation of the adhesive from the backing resulting in a useless product or in one that could be used only with difiiculty. In addition, the normally available hard grades of the metals formed sharp edges that tended to cut the skin of the users presenting grave danger of accidents. Recently, softer grades of the metals became available, which, however, continued to present anchoring difiiculties.

Even though there were these objections to earlier tacky and pressure-sensitive metal products, the need for such products was great and demand, though unsatisfied, continued. As normally tacky and pressure-sensitive adhesive products based on non-metallic backings developed it became more and more obvious that for any given thickness of a tape product the strongest possible tape would have to be based upon a metal backing. In view of the crowded spaces wherein adhesive tapes are frequently applied, for instance, in splicing cables, minimum thickness coupled with strength is of course of primary importance. Moreover, as to durability and permeability most adhesive tape backings of the prior art permitted some degree of moisture penetration and deteriorated under adverse climatic conditions with age. Here again only metallic backings provide a product satisfactory under the greatest variety of severe conditions. With increased utilization of high frequency currents the problem of providing satisfactory metal tapes, which provide efficient insulation for such currents, became even more important than previously.

Broadly stated, the object of the present invention is to provide products wherein-there is a firm, non-weakening bond between a metal backing and an adhesive coating. More particularly the object is to prepare normally tacky and pressure-sensitive metal-backed adhesive tapes wherein there is such a bond. Another object is to provide compositions adapted to bond adhesive compounds to metals. A further object is the provision of normally tacky and pressuresensitive adhesive tapes that are free of the objections against similar products of the prior art. Yet another object is the provision of a satisfactory normally tacky and pressure-sensitive adhesive tape that conforms readily to surfaces to I which it is applied, that is thin, and that has high strength and low moisture-permeability. Other objects will be apparent as the invention is more full described hereinafter.

In accordance with the invention a normally tacky and pressure-sensitive adhesive tape is prepared by coating a flexible metal sheet with a thin layer of a composition of. vinyl chloride acetate copolymer, acrylic-butadiene copolymer composed mainly (at least to the extent of fifty per cent by weight) of butadiene, and a minor amount of maleic anhydride, reacted preferably with one of the aforementioned copolymers. This primer layer is coated with another primer layer composed of acrylic-butadiene copolymer as described above and comprising an elastomer that is compatible with the elastomeric base of the normally tacky. and pressure-sensitive adhesive composition used. The normally tacky, and pressuresensitive adhesive may be applied directly to the surface of this second primer layer. A satisfactory normally tacky and pressure-sensitive adhesive product results wherein the adhesive is secured firmly to its backingand wherein there is no separation of the two layers even after long storage or during repeated use under adverse conditions.

While various grades of metal foil may be used in the production of normally tacky and. pressuresensitive adhesive tapes, for safety reasons the softest available grades which do not have sharp cutting edges appear most suitable. Where, as in'the case of aluminum, this soft grade is so weak as to make coating and handling difficult, half-hard and particularly quarter-hard grades will be preferred. The term half-hard means that the tensile strength of the metal is close to half-way between the hardest and the sofest commercial foil. Quarter-hard foil in turn has a tensile strength approximately half-way be zinc coated aluminum and tin are highly suitable for purposes of the invention.

3 In preferred embodiments of the invention each of the primer layers comprises a weight of 0.1 -0.5- ounce per square yard and the normally tacky and pressure-sensitive adhesive is applied to a spreading weight of ;75-4 ounces per square yard. Whileapplication of the layers by means 7 of heat, using, for instance, a calender or a hot metal coater is possible, the usual method of application comprises spreading from solvent at or above normal room temperatures and drying the coat at elevated temperatures, for instance, for

one to three minutes at 150-300 F.

In order to disclose the nature of the invention I Parts by weight Copolymer:.of'8.6% by weight vinyl chloride,

. 13% vinyl acetate and 1% maleic' anhy- .dride havingv a molecular weight of 16,000

(Staudinger viscosity,method). 10

Copolymer of.75.% by weight butadiene and 7 25% by weight acrylonitrile having a .HMooney viscosity of 50 measured under standard conditions V The above composition was dispersed in methyl ethyl'ketone'to a concentration of 20% by weight before application.

After drying of the coated'product for 2 minutes at 260F., 0.3 ounce per square yard of asecondprimer was applied which-was composed Part by weight Copolymer of '75-per centby weight butadiene -and 25 per cent by weight ofacr-ylonitrile as Copolymer of 75 per cent by weight butadiene and 25 per cent styrenehaving a Mooney viscosity of 90 to 110 1 (This had been dispersed to a concentration of 20 per cent in a solvent composed of half methyl ethyl ketone, half aromatic aliphatic or aromatic petroleum solvent such as toluol.)

This coating was dried in the same manner as the first coating and a normally tacky and pressure-sensitive adhesive composition based on natural rubber was applied by a reverse roll coater from solvent to a coating weight of 1.5 ounces per square yard. This adhesive composition was composed of the following parts by weight:

Parts Grizzly pale crepe rubber 6 Zinc oxide 5 Polyterpene (melting point 115 C.) 2 /2 Polyterpene (melting point 70 C.) 2 /2v Wool fat /z Diamyl hydroquinone antioxidant 0.1.

' After drying of the adhesive coating a metal baclg'ed normally tacky and pressure-sensitive tape resulted'that hada firm and permanent bond between adhesiveand metallic backing and that withstood repeated abuse of the product and storage-at high temperatures and humidities. In its applications the product provided a strong and eflicient moisture and vapor barrier protecting the weakened cable joints that were spliced by means of the tape.

Example II Soft lead foil having a thickness of three mils was coated to a coating weight of 0.4 ounce per square yard with the following first primer coat- Parts by weight Copolymer of 86% per cent by weight vinyl chloride, 13 per cent vinyl acetate and 1 per centmaleicanhydride having a molecular weight of 55,000 (asmotic method) 8 Copolymer of 60 per cent by weight butadiene and 40-per centby weight acrylonitrile having a Mooney viscosity ofmeasured under standard conditions -1 1 Theabove composition was applied after dispersion in acetone to a concentration of 20 per cent by weight. 7 7

After drying of the coated product for three 7 minutes at 300 F. 0.25 ounce per square yard of a secondprimer was applied that was, composed of:

V 7 Parts by weight Copolymer of 60 per cent by-weight butadiene and 40 per cent by weight acrylonitrile as above 1 Copolymer of per centby'weightbutadiene and 50 per cent by weight styrene having a Mooney viscosity of'50 (This had' been dispersed to a concentration of 20 per cent in a solvent composed of one-half toluene and'on'e-half aliphatic ketones.)

This coating was driedin the same manner as the first coatjing and a normaly tacky and pressureesensitive adhesive composition based on butadiene styrene rubber was applied in the same I manner as the adhesive composition of the first examplebut to a coating weight of 2ounce's per square yard. The composition was composed of the following parts by weight:

Parts Copolymer of 50 percent butadiene and 50 per cent styrene having aMooney voscosity "of 5.5 20 Glycerol ester of hydrogenated rosin 15 Tertiary amyl phenol formaldehyde 2 Diam-yl hydroquinone Afterdrying'o'f the adhesive coating a thoroughly satisfactory normally tacky and pressuresensi-tivemetal tape resulted.

Example III Soft aluminum foil having a thickness of two mils'wascoated to a coatingweight of 0.15 ounce per square yard with the following first primer coating: V e

- 7 Parts by weight Copolymer-cf 86 percent by weight vinyl chloride, 13sp'er cent vinyl acetateand one per 'cent maleic anhydride as above 2 Copolymer of '75 percent butadiene and 25 percent acrylonitrile as in Example I 1 (This formula had been dispersed to a concentration of l5'per cent'solids by weight in methyl ethyl ketone solvent.)

The coating was driedfor three minutesat 280 F. and thereafter 0%25 ounces per square yard of a second primer was applied. This second primer was composed of: 1

Parts by weight Copolymer of 60 per cent butadiene and 40 per cent acrylonitrile as above 2 Copolymer of 75 per cent butadiene and 25 per cent styrene as above 1 (This formula had been dispersed in toluol to a concentration 'of 15 per cent before application.)

This coating was dried in the same manner as the first coating and a normally tacky and pressure-sensitive adhesive composition based on butadiene styrene rubber was applied in the same manner as the adhesive compositions of the preceding examples. The composition was composed of the following parts by weight:

Parts Copolymer of 50 per cent butadiene and 50 per cent styrene having a Mooney viscosity of 90 2 Smoked sheet rubber 3 Zinc oxide 6 Polyterpene (melting point 70 C.) 2 Polyterpene (melting .point 115 C.) 2 Diamyl hydroquinone antioxidant 0.1 Petroleum oil plasticizer 1 The resulting product was satisfactory and passed all tests for vapor-permeability and anchorage of the adhesive coating.

Example IV (The above composition was dispersed in acetone to a concentration of 25 per cent by weight before application.) a

After drying of the coated product for three minutes at 300 F. 0.25 ounce per square yard was applied of a second primer composed of:

Part by weight Polyisobutylene having a molecular weight by the Staudinger method of 110,000 1 Copolymer of 60 per cent by weight butadiene and 40 per cent by Weight of acrylonitrile as above 1 Parts Polyisobutylene (Staudinger viscosity 100- 120) 3 Dehydrogened rosin gum e 1 Alicyclic petroleum oil 1 The resulting tape was as satisfactory as those of the earlier listed examples.

The following additional primer formulations may? be substituted for the second. primer in Example I:

. Example V Part by weight Crude natural rubber 1 Copolymer of 75 per cent by weight butadiene and 25 per cent by weight acrylonitrile as above Dispersed in solvent and spread as in Example 1.

Example VI Part by weight Balata rubber 1 Copolymer of 60 per cent by weight butadiene and 40 per cent by weight acrylonitrile as above Dispersed in solvent and spread as in Example I.

Example VII 7 Part by weight Copolymer of '75 per cent by weight butadiene and 25 per cent by weight methacry'lonitrile as above 1 Copolymer of 7-5 per cent by weight butadiene and 25 per cent styrene having a Mooney .viscosity of 90-110 1 Dispersed and spread as in Example I.

Example VIII Parts by weight Copolymer of 60 per cent butadiene and 40 per cent by weight butyl acrylate or propyl methacrylate or other acrylic as defined herein, as above 1 Copolymer of '75 per cent by weight butadime and 25 per cent by weight styrene having a Mooney viscosity of 90-110 1 Dispersed and spread as in Example I..

All of the above compositions and variations thereof wherein polyisobutylene is substituted for the rubber. other than the butadiene-acrylic copolymer may be used to satisfaction.

In the execution of the invention inert metals other than those shown specifically in the examples may be used and the primer is useful in connection with all metals that may be made into tough foils. The first primer coating may prefer- I ably comprise vinyl chloride acetate copolymer to the extent of fifty per cent or more of the weight of the composition and butadiene copolymer to the extent of fifty per cent or less of the composition. One-quarter to five per cent maleic anhydride reacted with one of the polymers present is preferably used. The butadiene copolymer of the first primer is preferably a copolymer of acrylonitrile but may be a copolymer of any of the other acrylics, namely the lower acrylates and substituted acrylates such as, for instance, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate and/or methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, etc. The vinyl chloride copolymer may comprise 65 to per cent by weight of vinyl chloride and five to 30 per.

1| connection compatible is intended to mean that arrears the two polymers when mixed; intimately, stored and subjected to moderate temperatures, say,. at about 200 F. will notshow'visible signs of separation. Throughout the specification and the claims, the term polymer is intendedv to include copolymers and interpolymers and the term copolymers interpolymers of two or more materials.

The preparation or type of the adhesives forms no part of. this invention and it has been noted that all normally tacky and pressure-sensitive adhesives when primed substantially in the manher (if this invention provide satisfactory normally--tacky and pressure-sensitive adhesive tapes. Normally tacky and pressure-sensitive adhesivecompositions are those which need no activation by heat or solvent but which adhere by mere pressure, and such compositions are well known in the art and described in the patent and other literature.

Many other variations of the above described invention will be apparent to those skilled in the art and are included in the inventive, concept.

i Iclaim:

1. Adhesive tape comprising a metal foil backing, a normally tacky and pressure-sensitive rubbery adhesive. coating thereon, a primer coating, adjacent to and in contact with said metal foil and comprising at least about fifty per centby weight of a copolymer comprising from about sixty five to about ninety five per cent by weight of vinyl chloride, and from about five to about thirty per cent vinyl acetate, copolymerized with each other andhaving a molecular weight of from about thirty thousand to about one hundred thousand, said primer coating comprising up to about. fifty per cent of copolymer of butadiene and at least one acrylic material selected from the group consisting of acrylonitrile, methyl acrylonitrile, methylacr-ylate, ethyl acrylate,.pro-

pylacrylate, butyl acrylate, pentyl acrylate,

said: second copolymer of butadiene, said primer also comprising, from about one quarter of a per centtoabout: five per cent of its weight. of maleic anhydride, and a second primer coating between and in, contact with said first primer coating and said adhesive coating and comprising'irom about A thirty-five to about eighty-five per cent by weight ofa copolymer of at least fifty per cent of the copclymer weight of butadiene and also comprising at least one of said acrylic materials, said second primer coatingalso comprising from about fifteen to about sixty-five per cent by weight of an oilsoluble elastomer that ishighly compatible with the rubbery baseoi said normally tacky and pressure-sensitive adhesive compositions and that iss elected from the group consisting of the copolymers of largely butadiene and; of styrene, natural rubber, balata rubber, and poly-isobutylene.

2. An adhesive tape according to claim 1 whereinsaid maleic anhydride is reacted-with at least one of the polymers in said first primer ooating.- p

3'. An adhesive tape according to claim- 1 wherein the acrylic material is acryonitrile.

-=4:'An,.adhesive'tape according to claim; 1'; wherein said metal foil is'aluminum foil.

5; An: adhesive tape according to claim 1 wherein each" primer coating comprises a weight of fromabout one-tenth of an ounce per square yard toabout one-half of an ounce persquare yard and whereinthe adhesive comprises from about three-quarters of an ounce to about four ounces per square yard.

6. An adhesive according to claim 1 wherein said oil soluble elastomer is polyisobutylene.

7'. An adhesive according toclaim 1 wherein said oil soluble copolymer is a copolymer or largely butadiene and of styrene.

8. Adhesive tape comprising an aluminum foil backing anormallytacky and pressure-sensitive highly compatible with the 'elastomeric base ofv the normally tacky and pressure-sensitive adhesive composition.

9 Adhesivetape comprising an aluminum foil backing, a normally tacky andpressure-sensitive adhesive coating thereon, aprimer coating adjacent to said foil and comprising substantially ten parts by weight of a copolymer comprising essentiallyv'inyl chloride and smaller amounts of vinyl acetatecopolymer'ized with each other, and comprising a minor percentage ofmaleic anhydride' reacted therewith; onepart by Weightof a copolymer 'of largely butadiene and of acrylonitrile, and a primer coating adjacent to said adhesive coating and comprising equal parts by weight of a' vcopolymer of largely butadiene and of acrylonitrile' and of a copolymer of largely butadiene: and ofstyrene that is highly com-- patible with the elastomeric base of the normally tacky and pressure-sensitive adhesive composie tion; eachof said primer coatings being appliedin a Weight of theorder of one-quarter of an ounce per square yard and said adhesive coating being applied in a weight of the order of three. quarters of an ounce to four ounces per square yard. 7

MARTIN L. SCHECHTMAN;

REFERENCES CITED The following references are of record inthe file of thispatent:

UNITED STATES PATENTS OTHER REFERENCES Vinylite Plastics Bonding, by Carbide and CarbonChemical Corp. (1944), pp. 10-12. 

9. ADHESIVE TAPE COMPRISING AN ALUMINUM FOIL BACKING, A NORMALLY TACKY AND PRESSURE-SENSITIVE ADHESIVE COATING THEREON, A PRIMER COATING ADJACENT TO SAID FOIL AND COMPRISING SUBSTANTIALLY TEN PARTS BY WEIGHT OF A COPOLYMER COMPRISING ESSENTIALLY VINYL CHLORIDE AND SMALLER AMOUNTS OF VINYL ACATE COPOLYMERIZED WITH EACH OTHER, AND COMPRISING A MINOR PERCENTAGE OF MALEIC ANHYDRIDE REACTED THEREWITH, ONE PART BY WEIGHT OF A COPOLYMER OF LARGELY BUTADIENE AND OF ACRYLONITRILE, AND A PRIMER COATING ADJACENT TO SAID ADHESIVE COATING AND COMPRISING EQUAL PARTS BY WEIGHT OF A COPOLYMER OF LARGELY BUTADIENE AND OF ACRYLONITRILE AND OF A COPOLYMER OF LARGELY BUTADIENE AND OF STYRENE THAT IS HIGHLY COMPATIBLE WITH THE ELASTOMERIC BASE OF THE NORMALLY TACKY AND PRESSURE-SENSITIVE ADHESIVE COMPOSTION, EACH OF SAID PRIMER COATINGS BEING APPLIED IN A WEIGHT OF THE ORDER OF ONE-QUARTER OF AN OUNCE PER SQUARE YARD AND SAID ADHESIVE COATING BEING APPLIED IN A WEIGHT OF THE ORDER OF THREE QUARTERS OF AN OUNCE TO FOUR OUNCES PER SQUARE YARD. 